signs of a cycled aquarium

Signs of a Cycled Aquarium: A Comprehensive Guide

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So you’ve got yourself a new tank and are excited to get some fish in it?

Not so fast! You’ll probably know that every fish tank needs an initiation period, or what’s known as ‘cycling’ before you can safely add any fish. This can take anywhere between two weeks to several months, so it’s a good idea to know the best way to go about it!

So, how will you know when your tank is fully cycled? Let’s find out…

But First Things First! What Is Cycling a Fish Tank?

Cycling is the common term for an essential initiation phase for a new tank, where beneficial bacteria known as nitrifying bacteria build ‘colonies’ or ‘cultures’ in the tank’s substrate and, most importantly, in the tank’s filter media.

Almost all aquarium filters have some kind of sponge that filters the water mechanically and biologically. The mechanical part is simply the sponge sieving out waste particles from the water.

The biological part is the nitrifying bacteria that live in the sponge, converting the toxic ammonia in the water into relatively harmless nitrates. This is an important part of the nitrogen cycle.

But for the biological filtration to work properly, there needs to be a large, healthy population of the beneficial, nitrifying bacteria living in the sponge. This can take some time in a new tank, and this period is known as… you should know it by now: Cycling!

3 Ways to Cycle An Aquarium

The Traditional ‘Fishless’ Way To Cycle an Aquarium

The traditional way to cycle a new fish tank is also the longest. The method is suitable for first-time fishkeepers because it doesn’t require you to have any fish or bacterial cultures to get things started. The only thing you need is A LOT of patience!

A new tank is set up with new substrate, rocks, plants, and treated tap water. A filter and heater are installed, turned on, and you add a safe source of ammonia, such as pure ammonia chloride. Then you are left to wait. And wait… And wait!

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Yes, this method of cycling an aquarium can take an unbearably long time. While if things go well, the cycling could be complete in 4 weeks, in other cases, you could be waiting up to 4 months!

It depends a lot on your water chemistry, which bacteria happened to hitch a ride into your tank with the gravel, rocks, and plants, and how effective your filter is at collecting up those all-important nitrifying bacteria!

Let’s look at some other methods, shall we?

Cycling Your Aquarium With Fish

Some aquarium owners prefer to do their initial tank cycling using live fish to produce ammonia, get the cycle started, and see whether they survive. I sometimes call this the ‘guinea pig fish method.’

If you think this cycling method sounds cruel, I’d have to agree with you. Even fairly low levels of ammonia can fatally poison fish, and subjecting them to a tank that isn’t yet properly established can easily result in some nasty symptoms and death.

People often use cheap, hardy species such as guppies for this purpose – a fish they don’t mind ‘sacrificing.’ But I wonder what the guppies would have to say about it!

Yes, it’s true that if everything goes swimmingly well and your tester fish survive, you’ll surely know that you can introduce other fish safely. But the rest of the time, you’d be causing needless suffering and often the death of an innocent fish.

What’s more, cycling with fish can also take an agonizingly long time. Aren’t there any better options?

Some Faster Ways of Cycling an Aquarium

Add Nitrifying Bacteria From an Existing Fish Tank

Phew! Yes, there is a much faster, more efficient, and more humane way of cycling your tank!

In an established aquarium, millions of beneficial bacteria exist within the filter media and gravel of the tank. To transfer them to the new tank, we need to place the existing filter, filter media, or substrate from the cycled tank into the new one.

This method does have its potential dangers, however. Introducing filter media or substrate from an existing tank poses the risk of introducing less-beneficial bacteria and pathogens to the new tank. For this reason, some hobbyists prefer to use safer methods…

Add Nitrifying Bacteria From a Bottle

Nitrifying bacteria can also be purchased as a culture in a bottle. This is added to the water and pure ammonia chloride to get the new bacterial colony up and running quickly.

The only slight downside of this method is that the live cultures are more costly than using an older filter sponge or gravel.

So, Which Cycling Method Is Better?

I’ve given some pros and cons of the above methods, so you can decide which is the most suitable.

For most hobbyists, I’d recommend the third and fourth options. If everything goes well with adding a bacterial culture, your tank can be cycled in two weeks.

The third method is a good bet if you have another aquarium in good condition, with no signs of pathogens. If you want to be sure that no other bacteria or viruses are entering your new tank, go for method number four.

3 Ways To Know That Your Tank Is Properly Cycled

signs of a cycled aquarium

After you’ve added your tank treatment, you’ll need to know whether your tank is properly cycled before adding your precious fish (not to mention any sacrificial throwaways!)

Test Your Water

Yes, it’s pretty obvious: The best way to know if your tank is properly cycled is to test it! You can buy accurate testing kits such as the well-known API Freshwater Test Kit to measure levels of ammonia, nitrites, and nitrates in your water, as well as pH.

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Your test results must show 0 ppm Ammonia, 0 ppm Nitrite levels, and less than 20ppm Nitrates to be considered fully cycled and safe to introduce fish.

It’s worth repeating the tests over a week before adding any fish to ensure the water conditions are truly stable. A healthy environment and clean aquarium water are ideal for your fish.

Testing strip kits are not highly recommended for initial testing since they are not so accurate. When your tank is fresh, you must ensure everything is safe!

See if Your Sacrificial Fish Are Still Alive

You probably understand I’m not the biggest guinea pig fish method fan. But if by some miracle, the poor fish has survived the ordeal and is still active and eating keenly, you can be pretty sure that your tank has completed the cycling process and that it’s safe to add your precious pet fish, such as a betta fish, into the tank.

Your Pet Fish Remain Healthy and Happy

Once you’ve passed the initial tests and introduced your pet fish, it’s time to observe them. If this is a betta fish, look for all the normal signs that your betta is healthy and happy.

He should be active and feeding well, with bright colors, shiny eyes, and glossy fins. We advocate for fish health and avoidance of high levels of nitrite and harmful bacteria in the aquarium.

If he shows signs of lethargy, loss of appetite, or reddish gills or streaks on his body, test your water – immediately! These are all symptoms connected with ammonia poisoning.

Now let’s look at how to remedy high ammonia levels if they occur.

3 Steps To Remedy High Ammonia Levels

Treat Your Fish

The most urgent task on your hands if your tank has suffered an ammonia spike is to treat your poisoned fish. Ammonia poisoning is extremely serious and can often lead to the death of fish. You must treat your fish as soon as possible to save them.

While ammonia poisoning causes fish to suffer hemorrhaging, secondary bacterial infections usually kill them. You should have moments of fishless cycling where you clean the aquarium and remove all fish excrement.

You must therefore remove the fish from the original tank into a quarantine tank to be treated with antibiotics or other antibacterial medication.

Never treat the fish in the original tank since antibacterial medications will only kill any remaining beneficial bacteria in your filter and thus make your ammonia problem worse.

Correct Your Water Parameters

Find out what happened to cause the ammonia spike in your tank. Make sure that your tank equipment is working properly and that your water pH is at a safe level.

Ammonia spikes can be caused when changes hit the colonies of nitrifying bacteria in temperature, pH, medication, or water chemicals.

Change 50 percent of your tank’s water, and make sure you dechlorinate the replacement water if it comes from the tap. Chlorinated water is one of the biggest causes of bacterial culture collapse and dangerous ammonia levels. Also, adjust the water’s pH if necessary.

Resurrect Your Bacterial Colonies

Ensuring your biological filter is working properly is important for good nitrogen cycling. Unless the spike was caused by a power outage or a temporarily blocked filter, it likely means that your nitrifying bacteria colonies are not doing their job properly and need to be boosted.

You must act fast by replacing the filter or filter media with an equivalent from an established tank or introducing nitrifying bacteria from a bottle.

Once the water parameters have been rectified and a healthy batch of nitrifying bacteria begin to work their magic, it may take up to 2 weeks for the ammonia level to return to zero.

Be sure to test your water thoroughly to ensure your tank is in a healthy and stable environment before reintroducing your fish.


Where Does Ammonia Come From?

Ammonia is a natural nitrogenous compound found in fish waste and other rotting organic matter like uneaten fish food and dead plant leaves.

Ammonia is also often added to municipal water supplies as a treatment agent. Since it’s highly toxic to fish, it’s one of the reasons it’s so important to properly treat tap water before adding it to your aquarium.

How Do I Keep Ammonia at a Safe Level in My Aquarium?

If your tank is well cycled and you follow responsible protocol for tank management, you shouldn’t have any problem with dangerous ammonia levels.

The problem only comes if your bacterial colonies are weakened by sudden changes in the tank’s chemistry or when you’re not keeping the tank clean enough.

Keep your stocking density to safe levels by following the golden rule of 1 inch of fish: 1 gallon of water, and be careful not to overfeed your fish.

Also, perform 10% partial water changes on a weekly basis, vacuum your tank and clean your filter regularly to avoid ammonia disasters.

Smaller tanks are more difficult to keep in equilibrium since there is less water to buffer any changes in the tank’s chemistry. I’d recommend an aquarium of at least 10 gallons if you’re starting out.

How Do I Keep Nitrites at a Safe Level in My Aquarium?

If you buy an API testing kit, it will tell you the concentrations of 3 nitrogenous compounds: Ammonia, nitrites, and nitrates.

Ammonia is fish’s most dangerous nitrogen compound, whereas nitrate is the safest. You can think of nitrites as the compound produced in the in-between stage in the nitrogen cycle, as ammonia is converted to nitrates.

Nitrites are also toxic to fish and should be kept to 0ppm in the water. Following all the same protocols to maintain safe ammonia levels should also keep nitrite at zero.

How Do I Correct High Levels of Nitrates in My Aquarium?

Nitrates are a much safer nitrogen compound than either ammonia or nitrites. Nevertheless, if they become too high (more than 20ppm), you may still need to reduce them to ensure a safe environment for your fish.

Live plants are a wonderful way of managing nitrate levels over longer periods since they love to absorb nitrates to grow. Plants that are well-fed with nitrates tend to have lovely lush-looking dark leaves.

In an emergency, you must simply do water changes and extra tank cleaning until the nitrate concentrations return to a safe level (0-20ppm).

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